Nature of Sound
Sound is a mechanical wave produced by vibrating sources. It requires a medium—solid, liquid, or gas—to travel. No sound in vacuum.
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Nature of Sound
Vibrating source and medium particles. Switch medium.
What is sound?
Sound is a mechanical wave: a disturbance that travels through a medium due to the vibration of particles. When a source (e.g. a speaker cone or tuning fork) vibrates, it pushes and pulls neighbouring particles, which in turn disturb their neighbours. The disturbance propagates as a wave, but the medium itself does not travel from the source to the listener—only the energy and the pattern of compression and rarefaction do.
Why sound needs a medium
Sound cannot travel through vacuum because there are no particles to vibrate and pass the disturbance along. In solids, liquids, and gases, particles are close enough to transfer the vibration. Sound generally travels fastest in solids (stiff, dense bonds), then liquids, then gases.
Why can you hear a bell inside a jar when air is present, but not after the air is pumped out?